LAARS NeoTherm NTV (Sizes 150–285 MBTU/h) - Service Manual - Manual (Page 72)

62 Service Manual NeoTherm 80 - NeoTherm 285
11. Note the two large wires running to this assembly.
The spark wire and the flame sense wire look alike.
The unit will not run if you reverse these wires.
Before removing the wires, mark the spark wire with
a piece of electrical tape. Also disconnect the green
ground wire.
12. Pull out the burner can. Figure C5-9 shows how
the can looks once it has been removed. The can
shown here is new, so it is completely clean. On a
used unit, you will see some soot or dust on the thin
metal vanes on the outside of the can. Blow soot or
dust off of the vanes using compressed air (50 psi
max.). Wipe out the inside of the can with a non-
detergent cleaner like Windex®.
Note - Be careful when handling the burner can.
The thin metal vanes are delicate, and can be dam-
aged easily.
13. Once the burner can has been removed, remove
the front of the heat exchanger. Undo the six 10mm
nuts. As you remove the burner door, note the posi-
tion of the large black gasket.
14. The flame sensor is mounted in the front cover of the
heat exchanger. Over time, this sensor can become
tarnished or coated. (This will happen more quickly
if the NT unit has been operating often at a low firing
rate.) The flame sensor has a protective coating.
Important! Do not use sandpaper, steel wool, or
emery cloth to clean the flame sensor. These mate-
rials will clean the sensor, but they will also remove
the protective coating. The sensor will work, but
only for a short time.
The best way to clean the flame sensor is to use a
dollar bill, as shown in Fig. C5-10. The paper used
in the bill is just abrasive enough to clean the sensor
correctly, without removing the protective coating.
Note - The white ceramic “refractory” material on
the inside of the heat exchanger cover is brittle, and
can be damaged easily. Handle the heat exchanger
cover carefully.
Fig. C5-9 - Burner can removed
Fig. C5-10 - Correct way to clean the flame sensor
Cleaning the Burner and Heat Exchanger (continued)
Fig. C5-11 - Inside of heat exchanger (new unit)
Refractory
material
C5
cont.